DE-OS 34 38 594 disclosed a control mechanism for a clutch in which the speeds of the engine and the input and output speeds of the transmission are detected and processed in an electronic clutch control for slip modulation of the clutch.
The slip control switch itself, which modulates the actuator for the clutch, takes place depending only on the input speed of the engine and the transmission. The output speed of the transmission, which is proportional to the velocity of the vehicle, is used only for determining the vehicle downtime or a sequence velocity.
However, in many transmission controls, especially in automatic transmissions for passenger cars, the transmission input speed is not directly known, since no adequate sensors are placed on the output shaft of the clutch or on the turbine shaft in the case of automatic transmissions with a hydrodynamic torque converter. But the output speed of the turbine or the clutch can obviously be calculated from the ever-present velocity of the vehicle which corresponds to the output speed of the transmission and from the equally known gear ratio in the transmission. But during a gear change, which lasts a certain period of time, the gear ratio is not defined so that the output speed of the clutch cannot be so simply calculated.